CAPE CANAVERAL -- The sort of mistake usually found in grade-school math homework
proved fatal to a $125 million NASA Mars probe.

A NASA investigation released Wednesday confirmed earlier reports that aerospace
contractor Lockheed Martin botched the design of critical navigation software for the
ill-fated Mars Climate Orbiter. While flight computers on the ground did calculations
based on pounds of thrust per second, the spacecraft's computer used metric system units
called newtons. A check to make sure the values were compatible was never done.

The mistake wasn't detected because of an embarrassing assortment of screw-ups at
NASA's Jet Propulsion Laboratory, the Pasadena, Calif., facility responsible for managing
the project.

"Our check and balances processes did not catch an error like this that should
have been caught," said Ed Weiler, NASA's associate administrator for space science.
"That is the bottom line. Processes that were in place were not followed."

The spacecraft was to go into orbit around Mars on Sept. 23, acting as a weather
satellite and relaying data to Earth from a sister probe scheduled to land on the Red
Planet next month. But the metric mistake caused the Climate Orbiter to drift slowly off
course as it fired its rocket engines about a dozen times to stabilize itself during a
nine-month, 416-million mile journey. The probe approached Mars at too low an altitude and
likely burned up in the planet's atmosphere.

Members of a team responsible for navigation weren't familiar enough with how to
operate the probe. Some lacked proper training. Others were overworked.

Concerns from the navigation team were not communicated to the project's management. A
final chance to fire the spacecraft's thrusters and put it back on course was missed. And
the faulty software was never properly tested.

"We clearly made a serious error," said Edward Stone, director of NASA's Jet
Propulsion Laboratory. "We must learn, and we must learn quickly, from the
loss."

The need to learn quickly is an urgent one. Investigators also uncovered a potential
problem with the Climate Orbiter's companion probe, Mars Polar Lander. The lander is
scheduled to touch down near the planet's south pole on Dec. 3.

Investigators are worried that hydrazine fuel used to power the Polar Lander's 12
thrusters might freeze in the bitter cold of space when the engines are turned on.

"The concern was that when the thrusters were asked to fire, the fuel flow to
those thrusters might be inhibited if we had any frozen [fuel] lines," Stephenson
said.

NASA engineers are optimistic they can solve the problem by activating heaters on the
spacecraft's fuel lines earlier than planned. All of the thrusters must work properly to
slow the spacecraft before its parachute is deployed. Otherwise, the Polar Lander will
crash on the Martian surface.

The probe is designed to look for water in the ice cap that covers Mar's south pole.

One of Mars Climate Orbiter's jobs was to relay data from the lander back to Earth.
That job will now be handled by another NASA spacecraft already in orbit around Mars.